Lead-acid cells and batteries utilize electrical connectors, most typically termed "bushings," to, in general, electrically connect various parts of the battery. Such bushings have a variety of configurations. However, one principal criteria is that the bushing be capable of efficiently conducting the current generated by the cell or battery.
One illustrative application for a bushing is in forming a terminal. More particularly, by way of one example, a bushing, typically embedded in the plastic cover, is generally annular in shape and is complementally sized to accept an upstanding post extending out of the cover in the terminal cell. In some applications, the bushing and post are then fused together to effect the electrical connection. In other applications, while the bushing and post are fused together, the terminal is offset from the annular opening of the bushing and is an integral part of the bushing.
In fabricating such bushings in the lead-acid battery field, a variety of techniques have been proposed. More particularly, the use of die casting and manual or automated gravity casting have been considered and used.
However, collectively, none of the methods previously used are entirely satisfactory. Indeed, a variety of problems exist.
Such problems range from the relative expense of equipment and/or molds to product issues such as gas entrainment in the resulting bushing. Such gas entrainment can lead to less than optimum electrical connections due to the increased electrical resistance which results. Even further, gas entrainment, and the resultant porosity in the molded bushing, can cause undesirable lead sputtering during subsequent fusion operations as well as enhancing potential electrolyte leakage problems.
Still further, prior methods raise a range of process-related issues. Such issues range from relatively high process expertise required when manual gravity casting techniques are used to drossing and lead-in-air problems.
An extremely important process issue concerns avoiding clogged valves and lines. More particularly, prior methods for making bushings have been plagued with problems due to clogged valves and lines due to solidified lead. After casting the bushing with the required quantity of lead or lead alloy, the lead supply must be cut off, typically by a valve. It has proven quite difficult to maintain such valves and the associated lines free from solidified lead.
Accordingly, despite the fact that a variety of casting techniques have been used over many years and the problems have, at least in general, been recognized, no satisfactory fabricating technique has been developed. There accordingly exists a need for a method of fabricating bushings which can minimize, if not eliminate, the problems attendant with prior techniques.
It is accordingly an object of the present invention to provide a more effective and efficient method for fabricating lead bushings for lead-acid cells and batteries.
Another object of this invention is to provide bushings and lead-acid cells and batteries utilizing such bushings which are less susceptible to gas entrainment and provide more effective electrical connections.
Yet another object of this invention lies in the provision of a method for fabricating such bushings which minimizes the need for process expertise and is more amenable to automation.
A still further and important object of the present invention provides a method for fabricating bushings which minimizes problems due to solidified lead. A related and more specific object provides a method that eliminates the need for using conventional valves.
Other objects and advantages of the present invention will be apparent as the following description proceeds.